I own a 3d printer which makes most of these projects look like the perfect fit for a 3d print (even when there are far simpler solutions). So that is what I'd do :)
Command Strips work similarly to the adhesive that holds batteries into phones. Very strong hold in the directions that count, but pulling the tab stretches them in a way that causes their structure to collapse and release. Must have for anyone who rents a house and doesn't want to put holes in walls etc, but I've also found them to be very useful for all sorts of off-label applications.
They're strong enough to hold heavy picture frames etc on to walls, lasting for years and still detaching easily. I'd certainly trust them to secure this little motor!